I'm using Lubuntu 14.04 with a Samsung Galaxy S3 running Android 4.3. Each time I connect my phone via USB, I get the following dialog:

Unable to open MTP device '[usb:002,023]'

A few moments later, I get the "Removable medium is inserted" dialog, prompting me to open in File Manager. After that, the phone is connected and fully accessible.

So MTP works. The problem is that I plug in my phone to charge every time I sit down, and unplug it every time I step away. Dismissing these two dialogs every time is a pain.

I would think the "Removable medium" dialog is the easier candidate. How do I tell Ubuntu to take no action and stop prompting me?

For the MTP error, all the discussion I can find is for people who can't get MTP working at all. For me, it's working, but only after throwing this initial error.

I've verified that my device is present in /lib/udev/rules.d/69-libmtp.rules